Electrical protective system



Oct. 24, 1950 H. KLEMPERER I 2,527,483

ELECTRICAL PROTECTIVEA SYSTEM Filed Aug. 7, 1946 Patented Oct. 24, 1950 UNITED STATES PATENT OFFICE ELECTRICAL PROTECTIVE SYSTEM Hans Klemperer, Belmont, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application August 7, 1946, Serial No. 688,909

3 Claims.

of said current-operated devices in the event of a short or overload condition.

Another object is to provide an electrical system having means for providing a predetermined waiting period after a short or overload occurs, during Which time Said energizing circuit is made inoperative, and on termination of said waiting period to again put said circuit in operation and thereafter provide a predetermined probationary period to determine whether the short or overload recurs.

Stil1 further objects of the present invention will appear to those skilled in the art as the description progresses both by reference thereto and the attached drawing, in which:

Fig. 1 is a Wiring diagram of one embodiment of the present invention; and

Figs. 2 and 3 are graphs showing the function reference to time.

Referring to Fig.'1, there is shown a test circuit comprising a source of alternating current I connected through a relay contact 33 to the primary I I of a high voltage transformer I2. The relay contact 33 is controlled by a circuit breaker B having a winding 3| for actuating an armature 12, said Winding being connected, at one end, to a bus 30, said bus, in turn, being connected to a source of alternating current. The other end of said winding 3l is connected through a relay contact 26 and conductor 32 to a grounded bus v'22.

The relay contact 26 is controlled by a relay IRA-I, said relay having a winding 23 which, when energized, as will be presently explained, actuates an armature to which said relay'contact 26 and three others are attached. One end of said winding is connected, by a conductor 4I, to a protective lamp 24, and from said lamp, by a conductor 42, to an adjustable arm 44 which is connected, at one end I4 thereof, to a load I5,

said load, in turn, being connected to the anode.

I6 of a discharge tube II, in this particular embodiment, a gaseous-discharging device. The

other end I8 of the secondary I3 is connected..v

by a conductor 20, to the grounded end ofthe resistor 2|, the high end of said resistor being connected to the cathode I9 of the tube II.

The circuit, as shown in the drawing, illustrates the position of the various components therein when the test circuit above described is adapted to select a potential acrossr a low resistfunctioning normally. Under normal conditions of operation of said test circuit, the current.

lected by the adjustable arm 44 and applied to. The lamp 24,

the winding 23 of relay R-I. serves to protect the winding 23 against excessive excursions of current therethrough.A n

The application of the selected amount of voltage to the winding 23 of relay R-I actuates the armature 25, causing the relay contact 26 to open and interrupt the current flowing in the winding 3I of breaker B. The interruption of current in said breaker B causes armature 'I2 to withdraw the relayl contact 33 from its normal position and, in turn, interrupt the ow of current I0 in the primary II of transformer I2.

' The last-named interruption of current deenergizes the test circuit of tube I1 and operation ceases.

At the instant relay R--I becomes energized, as above described, a number of operations occur substantially simultaneously.

When relay R-I is energized, the consequent deenergization of breaker B, in addition to causing the armature I2 to withdraw the relay contact 33 from its normal position, also causes said armature to withdraw a relay contact 34 attached thereto from its normal closed position. The opening of said relay contact734 causes the interruption of current in a counting circuit, including bus 30, relay contact `34, anl

electrically operated counter 35, a conductor 35, and grounded bus 22. The counter 35 may be of the type which, upon the interruption of current therethrough, trips a relay to actuate a counting mechanism. The counting circuit in this particular embodiment is incorporated for statistical purposes.

In addition to actuating the counting mechanism just described, the relay R--I, when energized, moves a relay contact 21, normally open, into closed position. It will be recalled that the opening of the relay contact 26 causes the cessation of operation of the tube I1. As a result, current ceases to iiow in winding 23 of relay Rf--I which would, if not otherwise provided for, result in said relay causing its attendant switches to assume their normal positions. However, because of the novel circuit arrangement of the present invention, the relay contact 21 closes a circuit which will supply the necessary current to maintain the relay R-I energized for a predetermined period of time, for reasons which will be explained below. The circuit just referred to includes the '115-volt bus 30, a conductor 31, a contact 38 and contact arm 39 of a timing relay T, `a conductor 40, theV relay contact 21, the winding 23, the conductor 43 and the` grounded bus 22. i

The timing relay T, the components of which are shown within the broken-line enclosure, is a Westinghouse type TK Universal Timing Relay and was selected for this particular embodiment. Other makes or types of relays performing similar functions may be used. The relay T includes a motor 46 attached to a shaft 'I5 and a pair of worm gears 13 and 14, for actuating a pair of rotatable members 15 and 16, having attached thereto, respectively, contact arms 39 and 6I. The arms 39 and 6I are adjustable with respect to each other and a plurality of contacts 3S, 59 and 62. Normally arm 39 is in closed position with respect to contact 38 and open with respect to contact 69. Arm 39 is adjusted so that a predetermined time elapses before it moves -into contact with contact 59. The length of time required for arm 39 to move from one position-to the other will be presently described and -will be designated herein as the waiting time.v The arm 6I is also adjustable and Ain this particular embodiment moves into contact position With Contact 62 at a period appreciably later than the time-set for contact of arm 39 with contact 69. AThe reason for this latter timing arrangement will also be explained below and will be designated herein as the probationary time. When motor 46 is energized, as will be presently explained, contact arm 39, when moved to contact 69 position, will remain in said position until motor 48 becomes deenergized. The same applies to contact arm 6i with respect to contact 62. Said contact arms are pulled back to normal, when motor 46 becomes deenergized, by a pair of springs (not shown), the pull oi said springs being appreciablyless than the pull of the energized motor 48. How the motor 46 becomes energized will be described below.

At. the instant relay R-I is energized, a relay contact .29, normally open, isy broughtinto closed position .by armature 25. The closing of the relay contact 29 causes the simultaneous completion of two circuits. First, the circuit for energizing motor 46 of relay T is completed from the 1,15- volt bus 39, through a conductor 45, to said motor 46, through a conductor 41, the relay contact 29, a conductor 48, and the grounded bus 22. Second, theA circuit for energizing a relay R-S has a winding d which when energized actuates anl armature 52, and it, in turn, controls the position of a relay Contact 55, normally open. rEhe flow of current for energizing the relay R-S is from the 1l5-volt bus 30, a conductor 49, the Winding 59, a conductor 5I, the relay contact 29, the conductor 4B, and the grounded bus 22. When the winding 50 is so energized, the relay R-S, through its armature 52, closes relay contact 55. The significance of this last-named a1'- rangement will be presently explained.

Up to this point of the description, relays R-I, T, and R-3 are energized. Relay R-I is maintained in an energized state for a period, called hereinbefore the waiting time period. During this period, the tube I1 remains deenergized for the reasons set forth above. The length of this period is determined by the amount of time required to properly cool oir tube l1. Consequently, arm 39 is set so that a period of time elapses, sufhcient to cool oi tube I1, before arm 39 moves to contact position 69.

At the conclusion of the waiting time period, motor 46, through the medium of its driving shaft 1D. and worm gear 1,3, rotates member 15. and its contact arm 39 to the position of Contact 9 9. The aforesaid rotation of arm 39 opens the relay RTI circuit and-thereby deenergizes same.' In addition to this last-named action, the de` energization of relay R-I causes the relay contacts 26, 21 and 29 to assume their normal positions. A fourth relay contactr 28, Vcontrolled by the actuation of the armature 25, said relay contact being open when therelay R/-I is energized, closes upon deenergization of said relay R,-I.

In the closed or normal position, relay'contact` 28 provides a path for the conduction of current from the l15volt bus 3D, through a conductor 68, through said relay-contact 28, the conductor 49, the contact arm 39, the contact 69 a conductor 51, a winding 58 of a relay R-Z, through a conductor 59 to the grounded bus 22. The current passing through said last-.named circuitr` tact 38 position and the circuit conducting the energizing current to the relay R-I is opened, the relay contact 26 falls in place, completing the circuit energizing the breaker B. When the breaker vB ,again becomes energized, it actuatesv the armature 12 and closes the relay contacts 33l and 34 attached thereto.

completes .the current circuit of primary II tube I1 again becomes operative,

Since the .de energization of the` relay R. I placesits attendant relay, contacts in their normal positions, the relay contact 29 willbe nor-l mally open and the motor 46 circuit would .or-

i and dinarily be interrupted. However, the energizdaw-V` tion of relay..R-3, asvv explained above, is held by an alternate circuit which includesthe volt bus 30, the conductor 49, winding 5,9 .of relay R-3, the relay. contact 53,0f a relay R.-4, a conductor 54, the relay contact 55, a conductor 56, and the grounded bus 22, The.. relay contact 53 of the relay 12.*.4 is normally closed and yin this position maintains `the motor energized by the ow of current from 115-volt bus 30, through the conductor .45,the motor49, the conductor 41,l

The relay contact 3.3

So far the relays lit- 2, Rf-3, breaker, B and timing relay T are maintained in an energized state. .This state is maintained for a period, hereinbefore referred to as the probationary time period, appreciably longer than the waiting time. If the tube IT operates normally through the entire probationary time period, at the conclusion thereof, the arm Bl will have moved into contact with the contact 62 thereby completing the circuit energizing the relay R-4. The now of current through this last-named circuit is from the 1,15-volt bus 30, through a conductor 63, a winding ,64, on the relay R-4, a conductor 65, the contact 62, the contact arm 6I, a conductor 66, and the -groundedrbus 22. When the winding 64 becomes thusenergized, it actuates armature 61 thereof and opens the relay contact 53 attached theretov Thetopening of the relay contact 53 interrupts simultaneously the flowr of current to the winding .50 ofthe relay R-3 and the motor 46 of the relayT..r When theimotor 46 is thus deenergized, ther-'contact arms 39 and 6l are snapped backto theirnormal positions by'ar 'spring member (not shown). As a result, alloflthe components, hereinbefore referredto, will assume the positions indicated in Fig. l.

A`Withialluof Atheacomponents in their normal positions, the tube il is again energized and the test, ywhich may be, for example, a life-span test, is continued until the tube l1 fails. It will be presently `explained what takes place when this event occurs.

`Thus far, the description of the circuit and its activities cover the situation in which the tube l1, atthe onset, fails or backfires, and, as a result of such an event, is deenergized. Then there is the waiting period during which the tube l1 cools off and subsequently the probationary period during which tube I1 is again energized. There will now be described a condition when the tube l1 backiiresy during the probationary period.

Let it be assumed that tube il has passed the waiting period and is now operating during the probationary period. However, during the probationary period assume also that tube I1 fails, and, as a result, rsaid vtube 'draws' anv excessive amount of current. The relay R|, which was deenergized at the conclusion of the waiting period, becomes again energized and is so energized during the period that relay T, breaker B, relays R-2 and R-3 are also energized.

As a result of relay Rf-l being energized during the probationary period, relay contact 26 of relay R-l opens and relay or breaker B becomes deenergized. Subsequently relay contacts 33 and 34 open their respective circuits, causing power supply' l0 to be interrupted and thus again deenergizing tube I1 and operating the counter 35. Relay contact. 2l' now closes the circuit which supplies current to the winding 23 of the relay R-l in the manner hereinbefore described and maintains the relay R-l energized when' current ceases to flow in tube I1.

Attention is called to the fact that the contact arm 39 of relay T is in the contact 69 position during the probationary'period and, as pointed out hereinbefore, maintains this position until the motor 46 of relay T is deenergized. Therefore, the contact arm 39 keeps the particular cirnated hereinbefore as the waiting period.

cuit supplying current to energize the relays Rf-I and R-2. 1

Also, as a result of relay R-l again becoming energized, the switch29 is drawn into closed position to complete the current supply circuit of motor 46. At the same time the relay R--3, which has been energized as described hereinbefore, provides a parallel current supply circuit to motor 46. However, as contact arm 6| continues to rotate, it will come into contact position with contact 62 thereby completing the circuit energizing relay R-4 as described earlier. When this occurs, the relay R-4 actuates its armautre 61 which, in turn, opens the normally closed relay contact 53. Under normal conditions, when tube I1 'opere ates properly during the probationary period, the

opening of the relay contact 53 would open thek motor 46 circuit and the entire circuit would return to normal as previously recited. However, despite the opening of the relay contact 53 of relay R-4, the motor 46 circuit remains operative because the relay contact 29 is in closed position and maintains a flow of current tosaid motor. Y

The ultimate result of the secondshort or overload occurrence in tube Il is to lock yin the entire circuit and maintain the test circuit inoperative until the tube I1 is removed. Upon removal of tube i1, switch 1I, which may be 'a momentarybreak type, is opened. This results in deenergization of the motor 46 and a return to normal position of the contact arms 39 and 6|. The return to normal position of the contact arms 39 and 6I of the timing relay T causes all of the relay contacts controlled by the relays Rf-I, R-2, R-3, R-4 and breaker B to return to their nor-` mal positions as indicated on the drawing in Fig. 1.

Actually, although the above events were de- Y but fail at vthe expiration of its life span, `thel same events .j ust described would transpire, except that the probationary time period would be eliminated as the recurrence of the tube failure would commence immediately after the conclusion of the waiting time period.

Although not indicated on the drawing, because; it is obvious to those versed in the art, means may be provided for determining the amount of time elapsed between each successive breakdown or between the reenergization of tube l1 during the probationary period and its final demise. Y Figs. 2 and 3 are graphs which illustrate the relation of operation of the various relays with In Fig. 2 the graph shows 'the relation of various components with respect to respect to time.

time when the tube I1 under test backres after i it has been put into operation for the nrst time.

This backre occurs with reference to time at point A of aforesaid graph and, as pointed out hereinbefore, relay R'-l is energized and remains so for the period between points A and B, desigbe seen from the graph that the powerror the period between points A and B has been inter-r rupted. At the time relay R-i becomes energized, relays T and R-3 also become energizedl as indicated in the graph and are active forsaid period of time between A and At the end of the waiting period or reference B, R-Z becomes energized, while relays T and R-S are still ener,-

gized. The aforesaid relays are maintained in, an energized state for the period between points" 7. Band C designated hereinbefore as the probationary time. It should be noted that between points B and C relay R-l is inactive, and in its normal position permits the power supply to become active as shown on the graph between points B and C. At the end of the period between points B and C, R-4 becomes energized asV described above and all of the other relays are deenergized and returned to their normal positions. Beyond point C if the tube behaves normally, the relays will remain deenergized and the life test to which tube l1 is being subjected will continue until the tube deteriorates. When thispoint is reached, the relays will again become energized and go through the two cycles above described.

In Fig. 3, the chart indicates a condition in which the tube backiires during the probationary period B to C. When this backfire occurs relay R--I will be energized at the instant the backfire in tube i's' occurs and the power interrupted as indicated on said graph. During the period between B and C relay R--2 being energized will cause relays T and R-E. to become locked in and power will remain interrupted until the necessary steps hereinbefore described have been taken.

It will be readily seen from the aforegoing descriptionA of the invention that there is provided an automatic device which, when once set into operation, will perform the duties or a human observer and thereby permit the ccntinuous test of a device under observation during periods of time when human attendance would entail an unnecessary expense. A `further feature of the device of the present invention is the elimination of possible re hazards which are present when a device under test causes an over-V load of a test circuit in the absence of a human observer.

`'I he particular embodiment of the present invention which has been illustrated and described was selected for the purpose or setting forth the principles involved. It will be obvious that the invention may be modified to meet various conditions which may arise in different specic uses and it is, therefore, intended to cover by the appended claims all such modifications which fali within the true spirit and scope of the present invention.

What is claimed is:

1. In combination with an electric currentoperated test circuit, means for interrupting the ow of current in said test circuit when said iiow of current exceeds a predetermined value, said interrupting means including a first normally energized solenoid-operated switch having a pair of normally closed contacts in said test circuit for controlling the now of current in said test circuit, a second solenoid-operated switch having a iirst pair of contacts connected in the circuit with the solenoid of said iirst-named switch and a power source for controlling the ow of current v through the solenoid of said rst-named switch,

means for connecting the solenoid of said secondnamed switch to said test circuit, whereby upon the occurrence of said excess new of current in said test circuit, said second-named switch, in

expiration of said last-named period for another predetermined period of time, and holding means forA maintaining said interrupting means operative if said second solenoid-operated switch is again energized by the occurrence of excess current in said test circuit during said last-mentionedy predetermined time, said holding means being deenergized by removal of said cause of excessive current flow.

2. In combination with an electric currentoperated test circuit, means for interrupting the flow of current in said test circuit when said flow of current exceeds a predetermined value, means for maintaining said interrupting means in operation for a predetermined period of time, means for restoring the flow of current in said test circuit at the expiration of said last-named period, said restoring means including a normally energized solenoid-operated relay having a contact for controlling the flow of current in said test circuit, a second relay having a contact electrically connected to the solenoid of said`r rstnamed relay for controlling the iiow of current through said solenoid, a timing switch connected` to the solenoid of said second-named relay for controlling the flow of current through the sole-v noid of said second-named relay, means for energizing said timing switch, whereby upon the expiration of said last-named period said timing switch causes said second-named relay to loperate said rst-named relay to restore the ow of current in said test circuit for anotherpredetermined period of time, and holding means for maintaining said interrupting means operative if said first-named means again interrupts the flow 0I current in said test circuit during said-mentioned predetermined time, said holding means beingdeenergized by removal of said cause of excessive current flow.

3. In combination with an electric currentoperated test circuit, means for interrupting the flow of current in said test circuit when said ow of current exceeds a predetermined. value, means for maintaining said interrupting means in operation for a predetermined period of time, means for restoring the low of current in said test circuit at the expiration of said last-named period, said restoring means including a normally energized solenoid-operated relay having a pair of contacts presently open in said test circuit for controlling the flow of current in said test circuit, a second solenoid-operated relay, a rst pairof contacts of said second relay being presently open and connected to the solenoid of said rst-named relay and a power source for controlling the ow of currentv therethrough, a sec.-

ond pair of contacts of said second relay being presently closed and connected to the solenoid of said second-named relay to control the flow of current through said last-named solenoid, a

motor-operated timing switch having a pair of contacts presently closed and connected in said circuit with the second pair of contactsY of said second relay to further control the ilow of cur-v rent-in the solenoid of said second relay, whereby upon the expiration of said last-named period, said timing switch opens its previously-mentioned contacts causing the contacts'of said second relay to reverse their positions and thereby cause the contacts of said rst relay to reverse their position and restore the flow of current, in said test circuit for another predetermined period of time, and holding means for maintaining said interrupting means operative upon said.- named means again interrupting flow of current 9 in said test circuit during said last-mentioned predetermined time, said holding means being deenergized by removal of said cause of excessive current flow.

HANS KLEMPERER.

REFERENCES CITED The following references are of record in the file of this patent:

Number 10 UNITED STATES PATENTS Name Date Borre Feb. 28, 1933 Nye Mar. 14, 1933 Fitz Gerald Jan. 16, 1934 Ellett May 28, 1935 Neher Sept. 17, 1935 Gamel Nov. 10, 1936 Dyer et a1. Sept. 20, 1938 Mc Cown June 14, 1949 

